Space key device
By improving the structural design of the spacebar mechanism and adopting components such as balance bar groups and reinforcing bar groups, the structural strength and stability of the keycaps are enhanced, solving the problems of spacebar deformation and excessive height, and realizing the thinness and lightness of laptop keyboards.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-16
- Publication Date
- 2026-03-31
AI Technical Summary
The keycap structure of the spacebar on laptops is relatively weak, causing deformation when pressing off-center areas, which affects the accuracy of the trigger signal. Furthermore, the current height of the spacebar cannot meet the requirements for thinner and lighter designs.
The design employs a substrate, thin-film circuit board, elastomer, keycap, scissor-switch unit, and balance reinforcement unit. By using balance bar group, reinforcement bar group, and intermediate reinforcement bar, the structural strength of the keycap is improved, reducing the keycap thickness to less than 0.5 mm and the overall height of the space bar device to less than 3.6 mm.
The structural strength and movement stability of the keycaps have been improved, meeting the requirements for thinner and lighter laptop keyboards, reducing the failure rate, and achieving an overall height of less than 3.6 mm for the spacebar device.
Smart Images
Figure CN224067586U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to an input device, and more particularly to a space bar device. Background Technology
[0002] As laptops continue to evolve towards thinner and lighter designs, the overall height of laptop keyboards must also be reduced. Taking the space bar on a laptop keyboard as an example, the space bar has a substrate extending along the length direction, a thin film circuit board disposed on the substrate, an elastomer disposed on the thin film circuit board, a keycap located at the top of the elastomer, two scissor legs pivotally connected between the keycap and the substrate, and two balance bars extending along the length direction and pivotally connected between the keycap and the substrate.
[0003] Because the spacebar has a large aspect ratio, the keycap has weak structural strength. When the user presses on a non-central part of the keycap, it is more prone to deformation, which affects the accuracy of the trigger signal. Although the structural strength and smoothness of the keycap can be enhanced by the stabilizer bar, the thickness of existing keycaps is greater than 0.6 mm. This results in the overall height of the spacebar being greater than 3.6 mm, and the overall height of the laptop keyboard is also greater than 3.6 mm, which does not meet the industry's requirement that the overall height of the spacebar and the laptop keyboard be less than 3.6 mm. Utility Model Content
[0004] The purpose of this invention is to provide a space bar device that can solve the aforementioned problems.
[0005] This utility model relates to a spacebar device suitable for laptop keyboards. The spacebar device includes a substrate, a thin-film circuit board, an elastomer, keycaps, a scissor-switch unit, and a balancing reinforcement unit.
[0006] The substrate extends along its length and includes a plate body, and a left front hook, a left rear hook, a right front hook, a right rear hook, a first left stop, a first right stop, a second left stop located to the right of the first left stop, and a second right stop located to the left of the first right stop. The first left stop has a front insertion hole and a rear insertion hole communicating with the plate body, the first right stop has a front insertion hole and a rear insertion hole communicating with the plate body, the second left stop has a front insertion hole and a rear insertion hole communicating with the plate body, and the second right stop has a front insertion hole and a rear insertion hole communicating with the plate body.
[0007] The thin-film circuit board is disposed on the top surface of the substrate along the length direction;
[0008] The elastomer is disposed on the top surface of the thin film circuit board and extends toward the top.
[0009] The keycap is located at the top of the elastomer. The keycap includes a body with a top surface and a bottom surface, and the distance between the top surface and the bottom surface is less than or equal to 0.5 mm. The keycap also includes a left front pivot, a left rear pivot, a right front pivot, a right rear pivot, a first front pivot arranged along the length direction, a first rear pivot arranged along the length direction, a second front pivot arranged along the length direction and located behind the first front pivot, a second rear pivot arranged along the length direction and located in front of the first rear pivot, and an intermediate connecting seat located between the second front pivot and the second rear pivot.
[0010] The scissor-switch unit includes a left scissor-switch module and a right scissor-switch module. The left scissor-switch module is pivotally connected between the left front pivot and left rear pivot of the keycap and the left front hook and left rear hook of the base plate. The right scissor-switch module is pivotally connected between the right front pivot and right rear pivot of the keycap and the right front hook and right rear hook of the base plate.
[0011] The balance reinforcement unit includes a balance bar assembly, a reinforcement bar assembly, and an intermediate reinforcement bar.
[0012] The balance bar assembly includes a front balance bar and a rear balance bar. The front balance bar has a long rod extending along the length direction and pivotally connected to a first front pivot of the keycap, a left rod and a right rod bending rearward from both ends of the long rod, a left insert bending to the right and inserted into the front insertion hole of the first left stop, and a right insert bending to the left and inserted into the front insertion hole of the first right stop. The rear balance bar has a long rod extending along the length direction and pivotally connected to a first rear pivot of the keycap, a left rod and a right rod bending forward from both ends of the long rod, a left insert bending to the right and inserted into the rear insertion hole of the first left stop, and a right insert bending to the left and inserted into the rear insertion hole of the first right stop.
[0013] The right insert rod of the rear insertion hole of the stop block;
[0014] The reinforcing rod assembly includes a front reinforcing rod and a rear reinforcing rod. The front reinforcing rod has a main rod body extending along the length direction and pivotally connected to a second front pivot seat of the keycap, a left rod body and a right rod body bending rearward from both ends of the main rod body, a left insert rod bending to the left side from the left rod body and inserting into the front insertion hole of the second left stop block, and a right insert rod bending to the right side from the right rod body and inserting into the front insertion hole of the second right stop block. The rear reinforcing rod has a main rod body extending along the length direction and pivotally connected to a second rear pivot seat of the keycap, a left rod body and a right rod body bending forward from both ends of the main rod body, a left insert rod bending to the left side from the left rod body and inserting into the rear insertion hole of the second left stop block, and a right insert rod bending to the right side from the right rod body and inserting into the rear insertion hole of the second left stop block.
[0015] The right insert rod of the rear insert hole of the right stop block;
[0016] The intermediate reinforcing rod is installed on the intermediate connecting seat of the keycap.
[0017] The spacebar device of this utility model has an inverted L-shaped cross-section along the top and bottom directions for the first left stop block and the first right stop block.
[0018] The spacebar device of this utility model has an inverted L-shaped cross-section along the top and bottom directions for the second left stop and the second right stop.
[0019] The space bar device of this utility model has a hollow rectangular intermediate reinforcing rod.
[0020] The beneficial effects of this utility model are as follows: through the balancing and reinforcing unit, the keycap as a whole obtains good support, effectively improves the structural strength of the keycap, reduces the thickness of the keycap body to less than or equal to 0.5 mm, makes the overall height of the space bar device less than 3.6 mm, and makes the overall height of the laptop keyboard less than 3.6 mm, thereby meeting the requirements of the industry. Attached Figure Description
[0021] Figure 1 This is a combined perspective view of one embodiment of the space bar device of this utility model;
[0022] Figure 2 This is a partial exploded and combined perspective view of the embodiment described above;
[0023] Figure 3 This is an exploded perspective view of the embodiment, showing that the embodiment includes a substrate, a thin film circuit board, an elastomer, a keycap, a scissor-switch unit, and a balancing reinforcement unit;
[0024] Figure 4 This is a perspective view of the substrate described in the embodiment;
[0025] Figure 5 This is an incomplete perspective view of the substrate in the described embodiment;
[0026] Figure 6 This is a partial exploded perspective view of the embodiment, showing a balance bar group and a reinforcement bar group of the balance reinforcement unit;
[0027] Figure 7 This is an incomplete perspective view of the embodiment, showing the scissor-leg unit, the balance bar assembly, and the reinforcing bar assembly mounted on the substrate;
[0028] Figure 8 It is a collection of Figure 7 A magnified view of a portion;
[0029] Figure 9 It is a collection of Figure 7 Another enlarged view of a portion;
[0030] Figure 10 It is a collection of Figure 1 A sectional view of line X-X in the diagram;
[0031] Figure 11 It is a collection of Figure 1 A sectional view of line XI-XI in the diagram;
[0032] Figure 12 It is a collection of Figure 1 A sectional view of line XII-XII in the diagram. Detailed Implementation
[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Before the present invention is described in detail, it should be noted that the relative positional terms used in the following description, such as "front-back direction X", "left-right direction Y", and "top-bottom direction Z", are based on the orientation shown in each figure, i.e., the normal use orientation. The front-back direction X is perpendicular to the left-right direction Y and the top-bottom direction Z.
[0034] See Figure 1 , Figure 2 , Figure 3 One embodiment of the space bar device of this utility model is applicable to a laptop keyboard (not shown). The embodiment includes a substrate 1, a thin film circuit board 2, an elastomer 3, a keycap 4, a scissor-switch unit 5, and a balance reinforcement unit 6.
[0035] See Figure 3 , Figure 4 , Figure 5The substrate 1 extends along a length direction, which in this embodiment is the same as the left-right direction Y. The substrate 1 includes a plate body 11, and a pair of left front hooks 12, a pair of left rear hooks 13 located behind the left front hooks 12 along the front-back direction X, a pair of right front hooks 14, a pair of right rear hooks 15 located behind the right front hooks 14 along the front-back direction X, a first left stop block 16, a first right stop block 17, a second left stop block 18 located to the right of the first left stop block 16 along the left-right direction Y, and a second right stop block 19 located to the left of the first right stop block 17 along the left-right direction Y. The first left stop block 16 is bent from the plate 11 toward the top, and its cross-section along the top-bottom direction Z is inverted L-shaped. The first left stop block 16 has a front insertion hole 161 and a rear insertion hole 162 that pass through along the left-right direction Y. Both the front insertion hole 161 and the rear insertion hole 162 are L-shaped and connect the first left stop block 16 and the plate 11. The first right stop block 17 is bent from the plate 11 toward the top, and its cross-section along the top-bottom direction Z is inverted L-shaped. The first right stop block 17 has a front insertion hole 171 and a rear insertion hole 172 that pass through along the left-right direction Y. Both the front insertion hole 171 and the rear insertion hole 172 are L-shaped and connect the first right stop block 17 and the plate 11. The second left stop block 18 is bent from the plate 11 toward the top, and its cross-section along the top-bottom direction Z is inverted L-shaped. The second left stop block 18 has a front insertion hole 181 and a rear insertion hole 182 that pass through along the left-right direction Y. Both the front insertion hole 181 and the rear insertion hole 182 are L-shaped and connect the second left stop block 18 and the plate 11. The second right stop block 19 is bent from the plate 11 toward the top, and its cross-section along the top-bottom direction Z is inverted L-shaped. The second right stop block 19 has a front insertion hole 191 and a rear insertion hole 192 that pass through along the left-right direction Y. Both the front insertion hole 191 and the rear insertion hole 192 are L-shaped and connect the second right stop block 19 and the plate 11.
[0036] The thin-film circuit board 2 is disposed on a top surface 111 of the plate body 11 of the substrate 1, extending along the length direction.
[0037] The elastomer 3 is disposed on a top surface 21 of the thin film circuit board 2 and extends toward the top.
[0038] See Figure 1 , Figure 2 , Figure 3The keycap 4 extends along the length direction and is located at the top of the elastic body 3. The keycap 4 includes a body 40, which has a top surface 401 and a bottom surface 402. The distance between the top surface 401 and the bottom surface 402 is less than or equal to 0.5 mm, that is, the thickness of the body 40 of the keycap 4 is less than or equal to 0.5 mm. The keycap 4 also includes a pair of left front pivots 41, a pair of left rear pivots 42, a pair of right front pivots 43, a pair of right rear pivots 44, a plurality of first front pivots 45 arranged along the length direction, a plurality of first rear pivots 46 arranged along the length direction, a plurality of second front pivots 47 arranged along the length direction and located behind the first front pivots 45, a plurality of second rear pivots 48 arranged along the length direction and located in front of the first rear pivots 46, and a plurality of intermediate connecting seats 49 located between the second front pivots 47 and the second rear pivots 48.
[0039] See Figure 2 , Figure 3 , Figure 7 The scissor-switch unit 5 is located between the base plate 1 and the keycap 4. The scissor-switch unit 5 includes a left scissor-switch module 51 and a right scissor-switch module 52. The left scissor-switch module 51 has an outer bracket 511 and an inner bracket 512 rotatably pivoted inside the outer bracket 511. The outer bracket 511 is pivotally connected to the left front latch 12 of the base plate 1 and the left rear pivot 42 of the keycap 4. The inner bracket 512 is pivotally connected to the left rear latch 13 of the base plate 1 and the left front pivot 41 of the keycap 4. The right scissor-switch module 52 has an outer bracket 521 and an inner bracket 522 rotatably pivoted inside the outer bracket 521. The outer bracket 521 is pivotally connected to the right front latch 14 of the base plate 1 and the right rear pivot 44 of the keycap 4. The inner bracket 522 is pivotally connected to the right rear latch 15 of the base plate 1 and the right front pivot 43 of the keycap 4.
[0040] See Figure 1 , Figure 2 , Figure 3 The balancing reinforcement unit 6 includes a balance bar group 60 located between the keycap 4 and the substrate 1, a reinforcement bar group 70 located between the keycap 4 and the substrate 1, and an intermediate reinforcement bar 80 installed on the keycap 4.
[0041] See Figures 6 to 10The balance bar assembly 60 has a front balance bar 61 and a rear balance bar 62. The front balance bar 61 has a long bar 611 extending along the length direction and rotatably pivotally connected to the first front pivot 45, a left bar 612 and a right bar 614 bent rearward from both ends of the long bar 611, a left insert 613 bent to the right from the left bar 612 and inserted into the front insertion hole 161 of the first left stop 16, and a right insert 615 bent to the left from the right bar 614 and inserted into the front insertion hole 171 of the first right stop 17. The rear balance bar 62 has a long rod 621 extending along the length direction and rotatably pivoted to the first rear pivot 46, a left rod 622 and a right rod 624 bent forward from both ends of the long rod 621, a left insert 623 bent to the right from the left rod 622 and inserted into the rear insertion hole 162 of the first left stop 16, and a right insert 625 bent to the left from the right rod 624 and inserted into the rear insertion hole 172 of the first right stop 17.
[0042] The reinforcing rod assembly 70 has a front reinforcing rod 71 and a rear reinforcing rod 72. The front reinforcing rod 71 has a main rod body 711 extending along the length direction and rotatably pivotally connected to the second front pivot seat 47, a left rod body 712 and a right rod body 714 bent rearward from both ends of the main rod body 711, a left insert rod 713 bent to the left from the left rod body 712 and inserted into the front insertion hole 181 of the second left stop block 18, and a right insert rod 715 bent to the right from the right rod body 714 and inserted into the front insertion hole 191 of the second right stop block 19. The rear reinforcing rod 72 has a main rod body 721 extending along the length direction and rotatably pivoted to the second rear pivot seat 48, a left rod body 722 and a right rod body 724 bent forward from both ends of the main rod body 721, a left insert rod 723 bent to the left from the left rod body 722 and inserted into the rear insertion hole 182 of the second left stop block 18, and a right insert rod 725 bent to the right from the right rod body 724 and inserted into the rear insertion hole 192 of the second right stop block 19.
[0043] See Figure 2 , Figure 10 The intermediate reinforcing rod 80 is installed on the intermediate connecting seat 49 and positioned on the bottom surface 402 of the keycap 4 body 40. In this embodiment, the intermediate reinforcing rod 80 is a hollow rectangular body.
[0044] See Figure 1 , Figure 2 , Figures 9 to 11The present invention mainly strengthens the structural strength of the keycap 4 by means of the balance reinforcement unit 6, so that the thickness of the body 40 of the keycap 4 is less than or equal to 0.5 mm, and when the user presses the keycap 4, the keycap 4 can still move horizontally and stably toward the thin film circuit board 2. Specifically, the front balance bar 61 of the balance bar assembly 60 has its long rod 611 extending along the length direction and located at the front end of the keycap 4 body 40, while the rear balance bar 62 has its long rod 621 extending along the length direction and located at the rear end of the body 40, thus supporting the front and rear ends of the body 40 along the length direction. Similarly, the front reinforcing bar 71 of the reinforcing bar assembly 70 has its main rod 711 extending along the length direction and located at the front end of the body 40 and behind the long rod 611, while the rear reinforcing bar 72 has its main rod 721 extending along the length direction and located at the rear end of the body 40 and in front of the long rod 621, thus supporting the front and rear regions of the body 40 along the length direction. Finally, the intermediate reinforcing bar 80 is located in the middle of the body 40, providing support to the middle region of the body 40 along the length direction. In this way, the body 40 is well supported as a whole, which can improve the structural strength of the body 40, and thus reduce the thickness of the body 40 of the keycap 4 to less than or equal to 0.5 mm.
[0045] When the keycap 4 is pressed, the left scissor-switch module 51 and the right scissor-switch module 52 of the scissor-switch unit 5, as well as the balance bar group 60 and the reinforcement bar group 70 of the balance reinforcement unit 6, enable the keycap 4 to move horizontally and stably toward the thin film circuit board 2. Furthermore, this invention reduces the thickness of the keycap 4 body 40 to less than or equal to 0.5 mm, while still maintaining sufficient structural strength and preventing deformation.
[0046] Furthermore, when the keycap 4 is pressed, the front balance bar 61 and the rear balance bar 62 rotate in a direction away from each other. The left insert 613 of the front balance bar 61 and the left insert 623 of the rear balance bar 62 rotate towards their apex, causing them to abut against the first left stop 16. Similarly, the right insert 615 of the front balance bar 61 and the right insert 625 of the rear balance bar 62 rotate towards their apex, causing them to abut against the first right stop 17. This restricts the rotational travel of the front balance bar 61 and the rear balance bar 62. The utility model improves the structural strength of the first left stop block 16 and the first right stop block 17 by making their cross-sections along the top-bottom direction Z in an inverted L shape. This increases the contact area between the first left stop block 16 and the left insertion rod 613 and the left insertion rod 623, and the contact area between the first right stop block 17 and the right insertion rod 615 and the right insertion rod 625. As a result, deformation of the first left stop block 16 and the first right stop block 17 due to concentrated stress points can be avoided, thus reducing the failure rate.
[0047] Similarly, when the keycap 4 is pressed, the front reinforcing rod 71 and the rear reinforcing rod 72 will rotate in a direction away from each other. The left insertion rod 713 of the front reinforcing rod 71 and the left insertion rod 723 of the rear reinforcing rod 72 will rotate towards the top and abut against the second left stop 18. The right insertion rod 715 of the front reinforcing rod 71 and the right insertion rod 725 of the rear reinforcing rod 72 will rotate towards the top and abut against the second right stop 19, thus limiting the rotational travel of the front reinforcing rod 71 and the rear reinforcing rod 72. The utility model improves the structural strength of the second left stop 18 and the second right stop 19 by making their cross-sections along the top-bottom direction Z in an inverted L shape. This increases the contact area between the second left stop 18 and the left insertion rod 713 and the left insertion rod 723, and the contact area between the second right stop 19 and the right insertion rod 715 and the right insertion rod 725. As a result, deformation of the second left stop 18 and the second right stop 19 due to concentrated stress points can be avoided, thus reducing the failure rate.
[0048] In summary, the advantages of this utility model's space bar device are explained below.
[0049] I. The spacebar device of this utility model, through the balance reinforcement unit 6 including the balance bar group 60, the reinforcement bar group 70 and the intermediate reinforcement bar 80, provides good support for the keycap 4 and effectively improves the structural strength of the keycap 4. Even if the thickness of the keycap 4 body 40 is reduced to less than or equal to 0.5 mm, the keycap 4 can still move horizontally and stably toward the thin film circuit board 2. Accordingly, the overall height of the spacebar device can be less than 3.6 mm, and the overall height of the laptop keyboard can be less than 3.6 mm. In fact, the overall height of the spacebar device of this utility model is 3.4 mm, and the overall height of the laptop keyboard is 3.4 mm, which meets the requirements of the industry.
[0050] Second, the present invention has an inverted L-shaped cross section along the top-bottom direction Z of the first left stop 16 and the first right stop 17, which can avoid deformation of the first left stop 16 and the first right stop 17 and reduce the failure rate.
[0051] Third, the present invention has an inverted L-shaped cross section along the top-bottom direction Z of the second left stop 18 and the second right stop 19, which can avoid deformation of the second left stop 18 and the second right stop 19 and reduce the failure rate.
[0052] The above description is merely an embodiment of this utility model and should not be construed as limiting the scope of this utility model. Any simple equivalent changes and modifications made in accordance with the claims and description of this utility model shall still fall within the scope of this utility model.
Claims
1. A spacebar device, suitable for notebook computer keyboard, comprising a substrate, a thin film circuit board, an elastomer, a keycap, a scissors leg unit and a balance reinforcing unit; characterized in that: the substrate extends along a length direction, and comprises a plate body, and a left front hook, a left rear hook, a right front hook, a right rear hook, a first left block, a first right block, a second left block located right to the first left block, and a second right block located left to the first right block, which are provided on the plate body, the first left block has a front insertion hole and a rear insertion hole communicating with the plate body, the first right block has a front insertion hole and a rear insertion hole communicating with the plate body, the second left block has a front insertion hole and a rear insertion hole communicating with the plate body, and the second right block has a front insertion hole and a rear insertion hole communicating with the plate body; the thin film circuit board is arranged on the top surface of the substrate along the length direction; the elastomer is arranged on the top surface of the thin film circuit board and extends towards the top end; the keycap is located at the top end of the elastomer, and comprises a body, the body has a top surface and a bottom surface, and the distance between the top surface and the bottom surface is less than or equal to 0.5mm, the keycap further comprises a left front pivot seat, a left rear pivot seat, a right front pivot seat, a right rear pivot seat, a first front pivot seat arranged along the length direction, a first rear pivot seat arranged along the length direction, a second front pivot seat arranged along the length direction and located at the rear side of the first front pivot seat, a second rear pivot seat arranged along the length direction and located at the front side of the first rear pivot seat, and an intermediate connecting seat located between the second front pivot seat and the second rear pivot seat; the scissors leg unit comprises a left scissors leg module and a right scissors leg module, the left scissors leg module is pivotally connected between the left front pivot seat and the left rear pivot seat of the keycap and the left front hook and the left rear hook of the substrate, and the right scissors leg module is pivotally connected between the right front pivot seat and the right rear pivot seat of the keycap and the right front hook and the right rear hook of the substrate; the balance reinforcing unit comprises a balance rod group, a reinforcing rod group and an intermediate reinforcing rod, the balance rod group has a front balance rod and a rear balance rod, the front balance rod has a long rod body extending along the length direction and pivotally connected to the first front pivot seat of the keycap, a left rod body and a right rod body bent towards the rear side from both ends of the long rod body, a left insertion rod bent towards the right side from the left rod body and inserted into the front insertion hole of the first left block, and a right insertion rod bent towards the left side from the right rod body and inserted into the front insertion hole of the first right block, and the rear balance rod has a long rod body extending along the length direction and pivotally connected to the first rear pivot seat of the keycap, a left rod body and a right rod body bent towards the front side from both ends of the long rod body, a left insertion rod bent towards the right side from the left rod body and inserted into the rear insertion hole of the first left block, and a right insertion rod bent towards the left side from the right rod body and inserted into the rear insertion hole of the first right block. The reinforcing rod set has a front reinforcing rod and a rear reinforcing rod; the front reinforcing rod has a main rod body extending along the length direction and pivoted to a second front pivot seat of the keycap, a left rod body and a right rod body bent from both ends of the main rod body toward the rear side, a left insertion rod bent from the left rod body toward the left side and inserted into a front insertion hole of the second left block, and a right insertion rod bent from the right rod body toward the right side and inserted into a front insertion hole of the second right block; the rear reinforcing rod has a main rod body extending along the length direction and pivoted to a second rear pivot seat of the keycap, a left rod body and a right rod body bent from both ends of the main rod body toward the front side, a left insertion rod bent from the left rod body toward the left side and inserted into a rear insertion hole of the second left block, and a right insertion rod bent from the right rod body toward the right side and inserted into a rear insertion hole of the second right block. The intermediate reinforcing rod is installed on an intermediate connecting seat of the keycap.
2. The space bar device of claim 1, wherein: The first left block has an inverted L-shaped cross section along the top-bottom direction, and the first right block has an inverted L-shaped cross section along the top-bottom direction.
3. The space bar device of claim 1, wherein: The second left block has an inverted L-shaped cross section along the top-bottom direction, and the second right block has an inverted L-shaped cross section along the top-bottom direction.
4. The space bar device of claim 2, wherein: The second left block has an inverted L-shaped cross section along the top-bottom direction, and the second right block has an inverted L-shaped cross section along the top-bottom direction.
5. The space bar device of claim 1, wherein: The intermediate reinforcing rod is a hollow rectangular body.